1. Field of the Invention
The present invention relates generally to the application of vision monitoring in traffic control systems, and specifically toward a system having a video monitoring system integrated within a traffic signal lamp.
2. Background Information
Efficient and effective traffic signaling systems are essential to meet the reliance on vehicular transportation that growing urban centers demand. Traffic signaling systems are effective when they accurately detect vehicle queues at intersections, and control traffic signals in response to the queues while maintaining vehicular throughput on the main routes.
A typical traffic signaling system is composed of a signal head, with three signal lamps (Green, Yellow, Red) in each vehicle approach direction. Signal lamp activation for each signal head in an approach direction is determined and controlled by a controller, typically housed in a control box at or near the signaled intersection. Rudimentary signaling systems employ fixed, or manually varied, timers that continuously cycle the signal lamps at the intersection based on time, irrespective of the presence or absence of vehicles at those intersections.
Traffic signaling systems with adaptive cycle timing are necessary in high vehicular throughput intersections. These systems use vehicle detection methods to trigger a signal cycle upon the detection of a vehicle queue in a stopped lane. The most common vehicle detection mechanism is an inductive loop embedded in the roadway surface that provides a vehicle detection signal to the traffic signal controller. Sequential inductive loop mechanisms are necessary to provide quantitative information on vehicle queues.
Inductive loop mechanisms are expensive to install, since the roadway surface must be cut, and wire conductors must be inserted into the roadway surface, and routed to the traffic signal control box. The inductive loop mechanisms are prone to failure, and, in the event of such a failure, the controller must resort to a default mode in which it cycles based on a timer.
A more modem method of controlling traffic signals is called “video traffic monitoring systems.” In this method, a vision system provides a computerized analysis of the traffic by analyzing the real-time video signal at the intersection. Video traffic monitoring system and methods employ the use of a video camera, coupled to an image processing apparatus, to detect one or more vehicles approaching the intersection. These video traffic monitoring systems can detect a single vehicle in an approach lane, or detect multiple vehicles in one or more approach lanes, and provide input that describes the queue to the traffic signal controller.
Typical video traffic monitoring systems are installed on dedicated posts at the sides of intersections, or as additional equipment on top of a signal head, or on the structure supporting the signal heads in the intersection. These video monitoring systems are costly to install due to the additional equipment, installation and the additional wiring and power requirements. Therefore, a more cost-effective method is to integrate the video traffic monitoring system directly into the traffic signaling lamp.